Manufacture of armor-piercing projectiles.



UNITED STATES PATENT OFFICE.

ROBERT ABBOTT HADFIELD, OF SHEFFIELD, ENGLAND. MANUFACTURE OF ARMOR-PIERCING PROJECTILES.

Specification of Letters Patent.

Patented Feb. 19, 1907.

To all whom it may concern:

Be it known that I, ROBERT ABBOTT HAD- FIELD, a subject of the King of Great Britain, and a resident of Sheffield, county of York, England, have invented an Improvement in Manufacture of Armer-Piercing Projectiles, of which the following description, in connection with the accompanying drawing, is a specification, like letters on the drawings representing like parts.

It has been found that owing to the introduction of hard-faced armor-plates, usually known as the "K. C. (Krupp cemented) type, armor-piercing projectiles of the ordina t e, even when capped, do not give 0 y good results, the projectiles often breaking up on the face of the plate or onl penetrating a short distance thereinto, or if perforating the plate doing so in such a broken condition as to cause little damage'.-i .In the course of my experimentsto improve the efiicienc of such projectiles I have discovered tat for successfully attacking plates ofthe character referred to the proje tils mustv be treated in amanner very different from that heretofore practiced.

My invention accordingly has for its object the production of novel and effective means for treating projectiles in the manufacture thereof to increase the efficiency thereof when used against hard-faced armor-plates.

The novel features of my invention will be fully described in the subjoined specification, and particularly pointed out in the following claims.

.In carrying out my invention the projectile ma with advantage be made of nickelchromium steel, such as described in my British Letters Patent Nos, 27,753, 27,754, and 27,755, all of'1897, but unless otherwise desired containing a lowerpercentage of carbonthan has usually been the case.

Preferably I use steel containing from decimal six five per cent.) of carbon and about 2% (two per cent.) each of nickel and chromium, manganese being kept as low as possible, as in the steel described in the pat ent referred to.

The carbon may vary from about 0.55% (decimal five five per cent.) to'0.7%, (decimal seven per cent.,)-or a higher percentage of carbon can be employed, provided a corresponding reduction in the hardening temperature is made.

My invention is applicable to either cast or (decimal five eight to forged projectiles, and by the former term is meant not only projectiles cast with a pow der-chamber, but also those cast solid, as in iron molds, and in which the chamber is subsequently formed by' boring. The latter method of producing east-steel chambered projectiles obviates any practical difficulty that may arise in casting projectiles with chambers of large capacity and having thin walls. It also has the advantage that the inner surface of the powder-chamber can be made bright and smooth, a matter of considerable im ortaneeinsome cases. So, too, the projecti emay be cast with a smaller chamber than is ultimately required and be afterward bored out to the requisite'dimensions.

In treating a cast or forged projectile in accordance with my present invention it is first subjected to a preliminary heat treatment or annealing process after it has been formed to shape, and it is then ready to be hardened. For the preliminary treatment the projectile is heated to a temperature of from, say, about 950 centigrade to 1,100 centigrade, and preferably to about 1,050 centigrade, and then cooled in air, after which it is reheated to a temperature of between- 700 centigrade and 800 centigrade, preferably about 750 centigrade, and then cooled slowly-as, for example, in sand or in the furnace, completing the preliminary heat treatment for the purpose of annealing or stiffening the projectile. The projectile is now ready to be hardened, and to this end it is heated uniformly by gradually heating in a furnace such, for instance, as is described in my British Patent No.- 3,543 of 1898, but in the present case the projectile is lowered farther into the furnace and heated uniformly all over to a temperature of substantially 865 centigrade, according to the caliber of the projectile and the purpose which it is desired it shall fulfil, the hardening temperature being increased with the caliber of the projectile and the thickness of the plate it is desired to perforate. The treatment just described has the double effect of enabling not only a high temperature to be reached for the ardening of the point and shoulder, but also by heating above the ordinary softening point, which is somewhere between about 740 centigrade to 780 cen tigrade, the wall of the projectile is stiffened and the material caused to possess a higher compression resistance. By raising the temperature to 820 centigrade and upward a much stifl'er material is secured, or, in other words, the hardness is increased. If a lower temperature is used-that is, lower than 820 contigrade-the projectile is too soft and is easily compressed when subjected to the firing test, whereas with the higher temperature referred to its compression strength is increased in a most remarkable manner. The temperature is carefully ascertained by an electrical or other suitable form of pyrometer which is inserted in the interior of the projectile to enable the temperature of both its interior and exterior to be noted, for as the projectile is evenly heated its interior is practically at the same temperature as its exterior. 'When the desired hardening temperature has been attained, the projectile is removed from the furnace and dipped, point downward, into the cooling liquid, preferably oil, to the desired zone depth.

if water be used as the cooling medium, it should be previouslyheated to such a temperaturesay, for example, about 60 centigradeas will give the same cooling effect as oil at ordinary atmospheric temperatures.

The projectile is dipped into the cooling medium only to the de th to which the projectile is required to be hardened, usually termed the zone depthfcr example, in a projectile of four inches diameter the zone depth-i. e., the. distance from the point rearward which is rcquiredto be hard-is usually about six inches,-corresponding to about one and onehalf calibers, and I prefer to make this the outside limit for the zone depth. In the case of a six-inch projectile designed to perforate a six-inch plate, the hardening zone may vary from about four and one-half to six and one-half inches. The projectile is then dipped into the cooling medium to the required zone depth. the remainder of the pro- I,

' phosphorus being lowsay, .05% (decimal -zero five per cent.) each. The projectile jectile extending out of the cooling medium, either for a portion or the whole of the time duringcooling down, to suit requirements. In the former case the complete immersion of the projectile in the cooling medium may take place after the partial immersion, with a sixinch projectile, has been effected for about twenty minutes, the time varying,rhowever, with the size of the projectile. The

rojectile may, however, be dipped overead 'i. e., the entire projectile--at any stage of the cooling-down step, according to the hardness desired.

By the treatment hereinbefore described I am enabled to obtain a peculiar combination of toughness and hardness, that portion of the projectile that is in the cooling medium becoming hardened, but not too hard, and that portion standing out of the cooling medium becoming very stiff at the portions adjacent the surface of the cooling medium and gradually decreasing in stiffness in an upjectile becoming tougher as the base is reached, where it is important that it should be tough.

It is usually found unnecessary in accordance with my present invention to pass a cooling liquid, such as oil or water, through the chamber of the projectile, as hereinbefore commonly practiced; but should it for any reason he found advisable to do this -it can be done to a much less extent and at a much later period of the hardening process than has heretofore been possible, a point of considerable advantage in the treatment, inasmuch as if such cooling medium is used it is used only after the temperature of the ro jectile has been reduced to a point at w 'ch it will cause no hardening or embrittling ac tion to take place. passed through the chamber.

The exact temperature to which the proj ectile should be heated for successful hardenmg and toughening, as hereinbefore de scribed, will vary according to the nature of the steel, the higher the percentage of carbon therein the lower the hardening temperature required-for example, for pro'ectiles made of nickel-chromium steel of the kind referred to the temperature will be about 750 centigrade, higher or lower temperatures being used according to the hardness desired.

By the improved process hereinbefore set forth projectiles can be produced which when capped will perforate. Krupp cemented armor unbroken. A

As an example of the practical carrying out of my invention very satisfactory results have been obtained with asix-inch projectile fired with a cap and made of nickel-chromium steel containing 0.6% (decimal six per cent.) of carbon, 2% (two er cent.) each of nickel and chromium, an one two per cent.) of silicon, sulfur and made from the steel was cast solid in an iron mold and was afterward heated gradually to a temperature of 1,050 centi ade, then cooled down in the air to the or inary temperature thereof and reheated to 750 centiade and cooled very slowly in the furnace. he projectile was then bored out and machined tothe required finished dimensions, after which the projectile was gradually heated all over in a furnace of the character hereinbefore referred to to a temperature of 865 centigrade, then taken out of the fur-.- nace and at once dipped point downward into oil for a zone depth of sixinches, such projectile capped, and then perforated a sixinch Krupp cemented plate at avelocity of nineteen hundred and eighty foot seconds Steam may thus be p 12% (decimal and was found in the rear of the plate in a condition for bursting.

Mechanical tests made by me on annealed 65 ward direction or toward the base, the pro- 1 nickel-chromium steel treated in accordance with my present invention show a very great increase in stiffness with increased temperatures over those heretofore employed. As a result of such tests I have found that a piece of such steel 0.7979 diameter which has been heated to a temperature of 800 centiade will, under a compression strain of one undred tons per square inch, shorten about thirty to thirty-four per cent, whereas if heated to substantially 865 centigrade the shortening will not be more than twenty-five per cent. A gradual increase in the resistance to compression is attained by the increase 1n temperature.

Having fully described my invention, what I claim as new, and desire to secure by Letters Patent, is-

1. In the manufacture of armor-piercing projectiles, heating and annealed nickelchromium steel projectile gradually and uni formly to a temperature of substantially 865 centigrade, and immediately dipping the heated projectile point downward to zone depth in a cooling liquid.

2. In the manufacture of armor piercing projectiles, heating the projectile to a temperature of from 950 centigrade upward to 1,100 centigrade, cooling it in air, reheating to a temperature of from 700 centigrade to 800 centigrade, and then cooling slowly, to anneal the projectile; then gradually and evenly heating the projectile to a temperature of from about 820 centi ade upward to about 920 centigrade, an dipping the heated projectile oint downward in a cooling liquid, to bar en the same.

3. In the manufacture of armor-piercing projectiles, heating the projectile to a temperature of about 1,050 centigrade, cooling in air to the temperature thereof, reheating to about 750 centigrade, and cooling slowly, to prepare the projectile for hardening; then gradually and evenly heating the prepared projectile to a temperature of about 865 centigrade, and immediately dipping the heated projectile point downward to zone depth in a cooling liquid.

4. An armor-piercing projectile of nickelchromium steel containing from 0.55 per cent. to 0.7 per cent. carbon, annealed, and hardened by a gradual and even heating to a temperature of from 820 centigrade and upward, and dipped point depth in a cooling liquid.

5. An armor-piercing projectile of nickelchromium steel containing not more than 0.7 per cent. of carbon, annealed and heat treated by gradually and evenly raising its temperature to about 865 ping point downward to zone depth in a coolin liquid, to harden the pro'ectile.

testimony whereof I ave signed my name to this specification in the presence of two subscribing witnesses. j ROBERT ABBOTT HADFIELD.

Witnesses:

G. H. HEMsoLL, 'ERNnsT RODGERS.

downward to zone centigrade, and dip- 

